So, without further ado, introducing volutus, a form of altocumulus or stratocumulus cloud that is typically a low, horizontal, detached tube-shaped cloud mass that often appears to roll slowly about a horizontal axis.

Volutus was the only new cloud species named, but multiple new accessory clouds, supplementary features and “special” clouds were also added to the atlas.

Stephen A. Cohn, a retired National Center for Atmospheric Research scientist, led the atlas revamp. He clarified that volutus is not a new type of cloud – cloud physics don’t change – but it is a phenomenon that didn’t fit in an existing classification.

Volutus clouds, which are detached, can form from the downdraft of a thunderstorm where rain-cool air rushes out in front of the shower. Usually that gust front is invisible, except for when it blows trees or leaves.

“But if that gust front reaches moister air, it can form a cloud,” Cohn said. “Sometimes it’s very spectacular, like with the Australian morning glory cloud.”

Some of the new cloud types were the result of man, including contrails and clouds formed from factory output.

Others included putting names to clouds that were already identified, but not formally named in previous version of the atlas.

A new cloud supplementary feature called fluctus is sometimes known now as the “Kelvin-Helmholz wave.” Courtesy International Cloud Atlas

Clare Nullis, a spokesman for the World Meteorological Organization, said the 30-year break between cloud updates was because of other priorities and limited staff and financial resources.

She said the atlas includes about 100 different cloud classifications.

“This was a major undertaking carried out by a special task force who worked over several years on this online version,” she said. “So not something that we could undertake lightly.”

The cloud atlas task force included scientists from every continent, except Antarctica, who study clouds that can be difficult to classify. Sometimes, existing classifications were put on clouds incorrectly by “observers who try to make an observation fit,” Cohn said.

Cohn notes in an article he wrote about the update how many things have changed since 1987.

“There have been numerous fundamental changes in our world since the most recent (atlas update) including the emergence of the Internet and the invention of cellular phones with cameras,” Cohn said. “Important advancements in scientific understanding, too have come about. The time is ripe for a new version.”

Cohn and his committee spent three years updating the atlas and creating a searchable database of cloud types so the average observer can identify the many variations and match what they are seeing in the sky to its formal name.

The atlas also offers short explanations on why the cloud forms.

Cohn said the online element is important because alternative atlases have filled the vacuum, threatening “the global standardization of cloud classification, which is one of the primary reasons for the existence of the International Cloud Atlas.”

Five new special cloud categories were added including homogenitus, which are contrails from airplanes. Courtesy International Cloud Atlas

Bruce Albrecht, a professor emeritus at the University of Miami’s Department of Atmospheric Sciences, was impressed by the organization’s new cloud atlas and its online presence.

“Cloud classifications have been going on a long time,” he said. “Some of these we’ve seen before, but just didn’t have a formal name for them.”

For example, the newly-named supplementary cloud “cavum” was called a punch-hole cloud by Albrecht when he was teaching.

Still, Albrecht said he took a photo a few years ago of what the new atlas has named asperitus clouds. He said there was no official name at the time.

“Clouds are centrally important to weather and climate,” Albrecht said. “If we didn’t have clouds, it would be a very different world.”

Newly-named cavum cloud has a well-defined home in a thin layer of a supercooled water droplet cloud. Courtesy International Cloud Atlas

Cohn said naming clouds is the first step to understanding them. If you look to the sky and see a cloud shaped like a cauliflower, is it just a pretty cloud?

“It’s so much better to be able to say, ‘That’s a growing cumulus cloud. Maybe it will become a cumulonimbus and there will be a big thunderstorm soon,'” Cohn said.

WMO Secretary-General Petteri Taalas said an updated cloud atlas is critical to serve as a training tool for meteorologists and pilots.

“More than two millennia ago, Aristotle studied clouds and wrote a treatise addressing their role in the hydrological cycle,” Taalas said in a press release. “And today, scientists understand that clouds play a vital role in the Earth’s energy balance, climate and weather.”

Storm 2016

About the Author

Kim Miller is the weather reporter for The Palm Beach Post.

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